fence something off
phrasal verb with fence verb [ I ] uk/fens/ us/fens/
用栅栏（或篱笆）隔开
to separate an area with a fence in order to stop people or animals from entering it
The hill had been fenced off to prevent animals from grazing on it. 已经用栅栏把那座山隔开了，防止动物吃那里的草。